Add SMTP headers, RedisRename function, and ISO code handling in Lua
Updated the SMTP client to include MIME and Content-Type headers. Added a 'RedisRename' function in the Redis client to rename an existing key. Enhanced ISO country code handling in the Lua geoip filter, it now stores all unique seen codes. Also, added the respective function name constants in const.go.
Signed-off-by: Christian Roessner c@roessner.co